Conformation and luminescence of isolated molecular semiconductor molecules

In this article, we describe, for the first time, direct comparisons of the detailed structures of two small molecule organic semiconductors, oligo(phenylenvinylene) (OPV) molecules with chains of five and six phenyl rings (5R-OC(8)H(17) and 6R-OC(8)H(17)), respectively, and their luminescence properties on a single molecule level. Our data originate from a combination of two powerful diagnostic tools in physical chemistry: ion mobility and single molecule fluorescence spectroscopy. These techniques enable us to precisely determine the shapes of isolated molecules in the gas phase and to correlate these structures to the emission from single molecules supported on bare glass substrates. The principal structural uncertainty in OPVs is the (possible) presence and location of cis-vinylene linkages (cis-defects) in the oligomer. The results show that the structures observed in the gas phase are strongly correlated to the categories of molecules observed in the single molecule polarization anisotropy measurements with nearly identical distributions for the two OPV molecules studied. Each category is also characterized by the luminescence efficiency of the molecules in each class, providing a direct correlation between the luminescence efficiency and the shape of the molecule. This combination of techniques provides a level of information far beyond that obtained via any other analytical technique.     

Reaction of η5-cyclopentadienylbis(triphenylphosphine)cobalt(I) with alkadiynes. Preparation and reactions of bicyclic cobalt metallocycles and a stable trimethylsilyl-substituted mono-complexed alkadiyne. Comments on the mechanism of cobalt-catalyzed alkyne cooligomerization

Reactions of η⁵-cyclopentadienylbis(triphenylphosphine)cobalt(I) (5) with several 2,n-alkadiynes (2) were investigated. Each of these reactions leads initially to a material in which one of the acetylene functional groups is π-coordinated to cobalt; this complex then undergoes conversion to a metallocycle. In cases where the two acetylene functions are connected by three- and four-carbon bridges (2b, 2c), metallocycles formed by intramolecular reaction of two acetylene functions in the same molecule may be isolated. In cases where the acetylene functions are joined by larger or smaller bridges, the reactions are more complex, and both inter- and intramolecular metallocycles are formed. Reactions of 5 with 1,8-bis(trimethylsilyl)-1,7-octadiyne (16) gives an isolable crystalline mono-acetylene complex (17), this material is stable in the solid state but undergoes conversion to metallocycle (18) in benzene solution. The relationship of these results to the mechanism of the CpCo(CO)₂-catalyzed benzocycloalkene synthesis is discussed; it is suggested that intramolecular metallocycles are intermediates in reactions leading to benzocyclopentanes and -cyclohexenes, but intermolecular metallocycles are probably involved in reactions leading to benzocyclobutenes.     

An assessment of pure,hybrid, meta,and hybrid‐meta GGA density functional theory methods for open‐shell systems: The case of the nonheme iron enzyme 8R–LOX

The performance of a range density functional theory functionals combined in a quantum mechanical (QM)/molecular mechanical (MM) approach was investigated in their ability to reliably provide geometries, electronic distributions, and relative energies of a multicentered open‐shell mechanistic intermediate in the mechanism 8R–Lipoxygenase. With the use of large QM/MM active site chemical models, the smallest average differences in geometries between the catalytically relevant quartet and sextet complexes were obtained with the B3LYP^* functional. Moreover, in the case of the relative energies between ⁴II and ⁶II , the use of the B3LYP^* functional provided a difference of 0.0 kcal mol^–1. However, B3LYP^± and B3LYP also predicted differences in energies of less than 1 kcal mol^–1. In the case of describing the electronic distribution (i.e., spin density), the B3LYP^*, B3LYP, or M06‐L functionals appeared to be the most suitable. Overall, the results obtained suggest that for systems with multiple centers having unpaired electrons, the B3LYP^* appears most well rounded to provide reliable geometries, electronic structures, and relative energies. © 2012 Wiley Periodicals, Inc.     

A new approach for the large-scale generation of mature dendritic cells from adherent PBMC using roller bottle technology

Background  

Human monocyte-derived DC (mDC) loaded with peptides, protein, tumor cell lysates, or tumor cell RNA, are being tested as vaccines against multiple human malignancies and viral infection with great promise. One of the factors that has limited more widespread use of these vaccines is the need to generate mDC in large scale. Current methods for the large-scale cultivation of mDC in static culture vessels are labor- and time- intensive, and also require many culture vessels. Here, we describe a new method for the large-scale generation of human mDC from human PBMC from leukopheresis or buffy coat products using roller bottles, never attempted before for mDC generation. We have tested this technology using 850 cm² roller bottles compared to conventional T-175 flat-bottom static culture flasks.